Where should I buy my roof?

[randomq]

I have to re-roof a small 8x16 ft shed roof structure (16x20 w/ overhangs).  Planning on 16 ft length metal roof, but the roof is not used for catchment so metal is not strictly required.  I have previously purchased overstock commercial roofing (heavy gauge) from a local contractor, but that supply has dried up.  Please share your experiences on where I should buy my roof, which gauge is solid enough, etc.  Also if you know anyone looking to sell some 16 ft metal roofing.

I tend to build like this: 2x_ rafters to code, 1/2" plywood, 30# roofing felt, plywood spacers for drainage, 2x4 purlins, HPM Pattern 7 (exposed fasteners), HPM screws.  Any suggestions for improvements?  I like having the plywood underneath for the noise reduction and to prevent condensation dripping inside.

This will be a non-air-conditioned living space.

Thanks for suggestions and ideas!

[Hotzcatz]

We bought some roofing from some folks in Mountain View who bring it in directly from China. (FB Marketplace) Seems a thinner gauge than the usual "min. 26 ga. pre-painted metal roof" and if you buy from them, be sure to count the sheets before taking them away. We bought 100 sheets and they were all wrapped in some metal cover and when we unwrapped them to use them about two months later, there are only fifty sheets there. No joy in getting the other half of the order, so 'caveat emptor'.

[randomq]

Thanks for the warning! I did go with the HPM pattern 7 again. Somehow it feels lighter, but I think my other surplus sheets were a higher grade from a commercial project.

Just a warning about the PVC roofing in the back corner of Home Depot, which the structure was originally roofed in: it cracked to hell when removing it, which I thought was due to age. But then some panels only a year old also cracked when some debris hit them. Don't trust your life to a PVC roof if you have tree limbs nearby! I may buy a sheet of the polycarbonate just to test and compare.

Also, the screws they sell with that roofing are complete junk. Every single one was rusty when removing the roof, which had leaked due to their failure. HPM painted stainless screws for the win!